JP4369332B2 - Transverse induction heating apparatus and transverse induction heating system - Google Patents

Description

  The present invention relates to a transverse induction heating apparatus disposed in a steel hot rolling line and a transverse induction heating system using a plurality of transverse induction heating apparatuses.

Conventionally, there is a solenoid type induction heating device that heats the entire width of the plate as means for reheating the central portion of the plate width of the material to be rolled. (For example, see JP-A-10-128424.)
In this solenoid type induction heating device, a predetermined time is taken so that only the surface is heated due to the skin effect, so that the thermal energy is sufficiently diffused inside the plate and the surface temperature becomes lower than the center of the plate thickness. And make the temperature distribution in the thickness direction appropriate.
JP-A-10-128424 (5th page, FIG. 1)

In the conventional solenoid type induction heating apparatus, the higher the heating frequency, the more the induced current flows on the surface of the material to be rolled, and the excessive temperature rise on the surface increases.
Further, the thicker the plate thickness, the larger the surface overheating relative to the inside.
For this reason, sufficient time for making the temperature distribution in the plate thickness direction appropriate before finish rolling is required, and there is a problem that the installation place of the heating equipment is restricted.
In addition, since the full width of the plate is heated, there is a problem in that useless power is consumed when only the central portion of the plate width is heated.
Also, when multiple transverse induction heating devices are installed from upstream to downstream of the steel hot rolling line, the power supply may trip after the plate tip of the material to be rolled passes through the upstream induction heating device. there were.

The present invention has been made to solve the above-described problems, and is a transformer in which the plate surface and the plate thickness center at the central part of the plate width of the material to be rolled are heated almost uniformly, and the excessive temperature rise on the plate surface is eliminated. An object of the present invention is to provide a berth type induction heating apparatus.
Moreover, it is a transverse type induction heating system in which a plurality of transverse type induction heating devices are installed from upstream to downstream of the steel hot rolling line, and the plate tip of the material to be rolled passes through the upstream induction heating device. An object of the present invention is to provide a transverse induction heating system capable of preventing a power supply from tripping later.

In the transverse induction heating apparatus according to the present invention, an inductor composed of an iron core and a coil wound around the iron core is sandwiched between a rough rolling mill and a finish rolling mill of a steel hot rolling line. In a transverse type induction heating apparatus that is disposed so as to face each other and heats the material to be rolled conveyed by a conveying roll by the inductor supplied with electric power from an AC power source, the plate width of the material to be rolled of the inductor The width of the iron core in the direction is made smaller than the sheet width of the material to be rolled and is arranged on the sheet width center line of the material to be rolled, the current penetration depth is δ (m), and the specific resistance of the material to be rolled is ρ (Ω -M), the permeability of the material to be rolled is μ (H / m), the heating frequency of the AC power source is f (Hz), the circumference is π, and the thickness of the material to be rolled is tw (m). When
The heating frequency of the AC power supply is set so that the current penetration depth δ of the following formula (1) satisfies the following formula (2), and the plate surface and the plate thickness center of the plate width central portion of the material to be rolled are It is heated almost uniformly.
δ = {ρ / (μ · f · π)} ^1/2 (1)
1.0 <{cosh (tw / δ) + cos (tw / δ)} / 2 <1.03 (2)

The transverse induction heating system according to the present invention is a transverse induction heating system in which a plurality of the above-described transverse induction heating devices are installed from the upstream side to the downstream side of the steel hot rolling line. AC power sources are individually connected to the inductors of the transverse induction heating apparatus, the heating frequency of the individual AC power sources is set to F1, F2,... Fn from the upstream side of the steel hot rolling line, and K = When 1.05 to 1.20, the heating frequency of each AC power source is set so as to satisfy the relational expression “F1> F2 × K>...> Fn × K ^n-1 ”. It is what.

According to the transverse induction heating apparatus according to the present invention, the iron core width in the plate width direction of the material to be rolled of the inductor is made smaller than the plate width of the material to be rolled and is arranged on the plate width center line of the material to be rolled. By selecting the heating frequency so that the current penetration depth δ of equation (1) satisfies the above equation (2), the plate surface / thickness center of the sheet width central portion is heated almost uniformly. And overheating of the plate surface can be prevented.
Further, according to the transverse induction heating system according to the present invention, it is possible to prevent the power source from tripping after the plate end of the material to be rolled passes through the induction heating device on the upstream side.

Embodiment 1 FIG.
FIG. 1 shows the configuration of a transverse induction heating apparatus according to Embodiment 1 of the present invention, and the relationship between the sheet width direction distance of the material to be rolled and the average temperature rise value that is induction heated by this transverse induction heating apparatus. FIG.
FIG. 2 shows the ratio (tw / δ) of the plate thickness (tw) to the penetration depth (δ) and the heat generation at the center of the plate thickness in the transverse induction heating apparatus according to the present embodiment shown in FIG. FIG. 3 is a diagram showing the relationship between the ratio of the heat generation density of the plate surface to the density (plate surface / plate center heat generation density), and FIG.
In FIG. 1 to FIG. 3, the material to be rolled 1 is conveyed by a conveying roll (not shown) between a rough rolling mill (not shown) and a finish rolling mill (not shown) of a steel hot rolling line. .
A pair (one set) of inductors 2 and 3 are arranged vertically so as to face each other with the material 1 to be rolled interposed therebetween. The inductors 2 and 3 are respectively composed of iron cores 2a and 3a whose width in the plate width direction of the material 1 to be rolled is smaller than the plate width of the material 1 to be rolled, and coils 2b and 3b wound around the iron cores 2a and 3a. Has been.

High frequency power is supplied from the AC power source 4 to the coils 2b and 3b, and the material to be rolled 1 is induction-heated by magnetic flux generated from the iron cores 2a and 3a.
By the way, although the iron core width of the inductors 2 and 3 is determined by the heating pattern, the core width is set to be equal to or less than a value obtained by subtracting 300 mm from the plate width of the material 1 to be rolled. The inductors 2 and 3 are arranged on the sheet width center line of the material 1 to be rolled, with the distance to 3a being at least 150 mm apart.
The “distance from the sheet width end portion of the material 1 to be rolled to the iron cores 2a, 3a” means the plate width end portion of the material 1 to be rolled and the iron core 2a in the direction parallel to the plate surface of the material 1 to be rolled. This is the distance to the outer peripheral surface of the iron core 3a (that is, the distance indicated by A or A 'in FIG. 1).
As a result, it was confirmed by experiments that the excessive temperature rise at the end of the plate width was almost eliminated and the iron core width region including the center portion of the plate width was heated as shown in FIG.

In addition, arranging the inductors 2 and 3 on the center line of the material 1 to be rolled includes one of the iron cores 2a and 3a including arranging the inductors 2 and 3 so that the centers of the inductors 2 and 3 coincide with the plate width center line. The inductors 2 and 3 are arranged at the center of the plate width so that the portion exists on the plate width center line. In the steel hot rolling line, the range of the plate width of the material 1 to be rolled is 600 to 1900 mm.
Therefore, the core widths of the iron cores 2a and 3a of the inductors 2 and 3 are preferably set in the range of 300 to 700 mm.

The following formula (1) shows a calculation formula for the current penetration depth δ (m) by induction heating in the transverse induction heating apparatus according to the first embodiment.
δ = {ρ / (μ · f · π)} ^1/2 (1)
Here, ρ is the specific resistance (Ω-m) of the material 1 to be rolled, μ is the magnetic permeability (H / m) of the specific rolled material 1, f is the heating frequency (Hz) of the AC power supply 4, and π is the circumference ratio. It is.
The relationship between the ratio of the current penetration depth δ according to equation (1) and the plate thickness tw of the material 1 to be rolled and the heat generation density ratio between the plate surface and the plate thickness center is shown in FIG. 2 and FIG. Yes.

Here, the ratio of the plate surface heat generation density to the plate thickness central heat generation density can be expressed by the following equation (3) using the plate thickness tw and the current penetration depth δ of the material 1 to be rolled.
Plate surface heat density / plate thickness center heat density
= {Cosh (tw / δ) + cos (tw / δ)} / 2 (3)
The temperature distribution in the plate thickness direction before heating is such that the plate surface temperature is lower than the plate thickness center due to the influence of heat dissipation.
Therefore, by setting the ratio of the plate surface heat generation density to the plate thickness center heat generation density (ie, the plate surface heat generation density / plate thickness center heat generation density) to be 1.03 or less, the plate surface can be heated almost uniformly. It is possible to prevent an excessive temperature rise.

In order to satisfy this relationship, the frequency may be selected so that the relationship between the sheet thickness tw of the material to be rolled 1 and the current penetration depth δ satisfies the following expression (2).
1.0 <{cosh (tw / δ) + cos (tw / δ)} / 2 <1.03 (2)
In the steel hot rolling line, the specific resistance ρ of the material to be rolled 1 processed at a predetermined heating temperature is about 120 μΩ-cm, and the relative permeability is 1.
Accordingly, the heating frequency of the material 1 to be rolled is 413 Hz for tw = 25 mm, 287 Hz for tw = 30 mm, and 161 Hz for tw = 40 mm. The ratio of the surface heat generation density is 1.03 or less, so that heating can be performed almost uniformly in the thickness direction of the plate, and overheating of the plate surface can be prevented.

FIG. 4 is a diagram for explaining the heat generation density distribution in the plate thickness direction of the transverse induction heating device and the solenoid induction heating device.
In the figure, 5 indicates the characteristics of the solenoid type induction heating apparatus, and 6 indicates the characteristics of the transverse type induction heating apparatus.
As shown in characteristic 5, the solenoid type induction heating device theoretically has a heat generation density of 0 at the center of the plate thickness, and heat generation concentrates on the plate surface.
On the other hand, the transverse induction heating apparatus can make the heat generation distribution substantially uniform with respect to the distance in the plate thickness direction as shown in the characteristic 6 by selecting an appropriate frequency.

In the first embodiment, the inductors 2 and 3 are described as having a pair (one set) arranged on the sheet width center line of the material 1 to be rolled. However, a plurality of sets (for example, 2 sets) are arranged in the traveling direction of the material 1 to be rolled. The inductors 2 and 3 are disposed at the same position in the sheet width direction or at the positions slid to the left and right, so that it is possible to heat with the optimum heating pattern even if it corresponds to the material 1 to be rolled having different sheet widths.
In the first embodiment, the inductors 2 and 3 are each described as having one magnetic pole. However, the same effect can be expected when a plurality of inductors having two or more poles are used.
Further, in the first embodiment, the AC power supply 4 generates high-frequency power, but the formula (2) can also be satisfied as a commercial frequency power supply of 50 Hz or 60 Hz.

As described above, the transverse induction heating apparatus according to the present embodiment is configured to heat the inductors 2 and 3 including the iron cores 2a and 3a and the coils 2b and 3b wound around the iron cores 2a and 3a. An inductor which is arranged so as to face the rolled material 1 between the rough rolling mill and the finish rolling machine of the rolling line, and is supplied with electric power from the AC power supply 4 by the rolled material 1 conveyed by the conveying roll. In the transverse induction heating apparatus heated by 2, 3, the core width in the plate width direction of the material 1 to be rolled of the inductors 2, 3 is made smaller than the plate width of the material 1, and the center of the plate width of the material 1 is rolled Arranged on the wire, the current penetration depth is δ (m), the resistivity of the material 1 to be rolled is ρ (Ω-m), the magnetic permeability of the material 1 is μ (H / m), and the AC power source 4 is heated. The frequency is f (Hz), the circumference is π, and the thickness of the material to be rolled is tw. When (m) is set, the heating frequency of the AC power supply 4 is set so that the current penetration depth δ of the following formula (1) satisfies the following formula (2).
δ = {ρ / (μ · f · π)} ^1/2 (1)
1.0 <{cosh (tw / δ) + cos (tw / δ)} / 2 <1.03 (2)
As a result, the transverse induction heating apparatus according to the present embodiment can heat the plate surface / thickness center at the center of the plate width to be rolled substantially uniformly, and can prevent overheating of the plate surface.

Embodiment 2. FIG.
FIG. 5 is a diagram for explaining the configuration and operation of a transverse induction heating apparatus according to Embodiment 2 of the present invention.
As shown to Fig.5 (a), the to-be-rolled material 8 is conveyed by the conveyance rolls 7a and 7b between the rough rolling mill (not shown) and the finish rolling mill (not shown) of a steel hot rolling line. Yes.
A pair of inductors 9 and 10 each having two (plural) magnetic poles are arranged so as to face each other with the material 8 to be rolled interposed therebetween.
The inductors 9 and 10 are respectively composed of iron cores 9a and 10a whose width in the plate width direction of the material 8 to be rolled is smaller than that of the material 8 to be rolled, and coils 9b, 9c, 10b and 10c wound around the magnetic poles. It is configured.

The coils 9b, 9c, 10b, and 10c are supplied with high-frequency power from an AC power source (not shown), and the material to be rolled 8 is induction-heated by the magnetic flux generated from the magnetic poles of the iron cores 9a and 10a.
The core widths of the inductors 9 and 10 are set to be equal to or less than the value obtained by subtracting 300 mm from the plate width of the material 8 to be rolled, as in the first embodiment, and the iron cores 9a and 10a are arranged on the plate width center line of the material 8 to be rolled.
In such a configuration, the AC power source (not shown) was heated under the setting conditions of a frequency (that is, heating frequency) of 150 Hz, a plate thickness of the material to be rolled 8 of 40 mm, a conveyance speed of 60 mpm, and an average temperature increase of 20 ° C. At this time, as shown in FIG. 5C, the plate surface being heated and the center of the plate thickness are heated substantially uniformly.

Here, when the material to be rolled is heated with the solenoid coil in the solenoid induction heating apparatus under the same conditions as the transverse type, the plate surface is large without almost raising the temperature at the center of the plate thickness while the material to be rolled passes through the solenoid coil. Raise the temperature.
The plate surface is overheated at 52 ° C, which is about 2.6 times faster than the average temperature rise value of 20 ° C.
As shown in FIG. 5 (b), the heat distribution of the material 8 to be rolled spreads from the portions facing the inductors 9 and 10, and in some cases reaches the transport rolls 7 a and 7 b arranged before and after the inductors 9 and 10. .
For this reason, there is a possibility that a spark occurs when the current flowing through the material 8 to be rolled comes into contact with the transport rolls 7a and 7b.

In order to prevent this, the surfaces of the transport rolls 7a and 7b are coated with an electrically insulating member such as a ceramic paint, for example, to prevent the current flowing in the material to be rolled 8 from flowing into the transport rolls 7a and 7b.
FIG. 6 is a diagram showing plate temperature histories before and after heating by a transverse type induction heating device and a solenoid type induction heating device.
In the solenoid type induction heating apparatus, it takes 20 seconds or more and 20 m in terms of distance for the plate surface and the plate thickness center to converge at a temperature rise set temperature of 20 ° C. at a conveyance speed of 60 mpm.
In contrast, the transverse induction heating apparatus converges within a few seconds.

Embodiment 3 FIG.
FIG. 7 is a diagram showing a coil connection of a transverse induction heating apparatus according to Embodiment 3 of the present invention.
In FIG. 7, the AC power source 4 is the same as that of the first embodiment, and the material to be rolled 8 and the inductors 9 and 10 are the same as those of the second embodiment.
In FIG. 7A, coils 9 b, 9 c, 10 b, and 10 c of the inductors 9 and 10 are connected in series and are connected to the AC power supply 4 and the matching capacitor 11.
7B, coils 9b and 9c of an inductor (upper inductor) 9 arranged on the upper side of the material 8 to be rolled are connected in series, and a coil 10b of an inductor (lower inductor) 10 arranged on the lower side. , 10c are connected in series.
The upper coils 9 b and 9 c of the material to be rolled 8 and the lower coils 10 b and 10 c are connected in parallel to the AC power source 4.

As shown to Fig.7 (a), when all the coils 9b, 9c, 10b, and 10c of the inductors 9 and 10 are connected in series, the inductors 9 and 10 are not symmetrically arranged up and down of the to-be-rolled material 8. However, the currents flowing through all the coils 9b, 9c, 10b, 10c are the same, and the electric losses of the inductors 9, 10 are equal.
On the other hand, as shown in FIG. 7B, when the coils 9b and 9c of the inductor 9 and the coils 10b and 10c of the inductor 10 are connected in parallel, the impedance of the coil closer to the material to be rolled 8 is small. Since a large amount of current flows, the electrical loss of the inductor closer to the material 8 to be rolled increases.

FIG. 8 is a diagram showing the electrical loss with respect to the gap between the material to be rolled 8 and the iron core of the upper inductor 9 and the iron core of the lower inductor 10.
8, (a) is the case where the gap between the iron core of the upper and lower inductors 9 and 10 and the material 8 to be rolled is equal to 90 mm, and (b) is the gap between the iron core of the upper inductor 9 and the material 8 to be rolled 50 mm. The gap between the iron core of the lower inductor 10 and the material 8 to be rolled is 130 mm, and the connections of the coils 9b, 9c, 10b, 10c are as shown in FIG. 7 (a). The gap with the material 8 is the same as that shown in FIG. 7B, and is shown in FIG. 7B in which the coils 9b and 9c and the coils 10b and 10c are connected in parallel.
FIG. 8 shows a comparison under conditions where the average temperature rise of the material 8 to be rolled becomes equal.
When the gaps between the iron cores 9a and 10a of the upper and lower inductors 9 and 10 and the material 8 to be rolled are equal, the electrical losses of the inductors 9 and 10 are equal as shown in FIG.

On the other hand, when the upper coils 9b and 9c and the lower coils 10b and 10c are connected in series as shown in FIG. 7A, the inductors 9 and 10 are arranged symmetrically with respect to the material 8 to be rolled. Even if not, since the currents flowing through all the coils 9b, 9c, 10b, and 10c are the same, the electric losses of the inductors 9 and 10 are substantially equal.
When the upper coils 9b and 9c and the lower coils 10b and 10c are connected in parallel as shown in FIG. 7B, the loss on the upper inductor 9 side with a small gap as shown in FIG. The loss becomes larger than in the case of connection as shown in FIG.
As described above, when the upper coils 9b and 9c and the lower coils 10b and 10c are connected in parallel, a large amount of current flows through the coils 9b and 9c on the side close to the material 8 to be rolled, so that the electrical loss of the inductor 9 on the near side is reduced. Since it becomes large and the cooling capacity of the coil is insufficient, the current that can be passed through the coil is limited, and the temperature rise value of the material 8 to be rolled may be limited.
On the other hand, as shown in FIG. 7A, the electric losses of the inductors 9 and 10 can be made substantially equal by connecting all the coils 9b, 9c, 10b and 10c in series.

Embodiment 4 FIG.
FIG. 9 is a diagram showing a configuration of a transverse induction heating apparatus in Embodiment 4 of the present invention.
In the figure, the material 1 to be rolled, the inductors 2 and 3 and the AC power source 4 are the same as those in the first embodiment.
In FIG. 9, a carriage 12 that is movable in the plate width direction of the material 1 to be rolled is disposed. The inductors 2 and 3 are arranged on the carriage 12 via lifting means 13 and 14 so as to face each other with the material 1 to be rolled interposed therebetween, and can be individually raised and lowered.
The coils 2 a and 3 a of the inductors 2 and 3 are connected to the AC power supply 4 via matching capacitors 15 and 16 disposed on the carriage 12. The matching capacitors 15 and 16 may be installed separately from the carriage 12.
In the transverse induction heating apparatus configured as described above, the inductors 2 and 3 disposed above and below the material to be rolled 1 are moved up and down by the lifting and lowering means 13 and 14, so that each inductor 2 and 3 and the material to be rolled are The gap with 1 can be adjusted arbitrarily.

FIG. 10 shows the increase in the plate thickness direction when the gap between the material 1 to be rolled and the iron cores 2a and 3a of the inductors 2 and 3 arranged above and below is changed in the transverse induction heating apparatus in the fourth embodiment. It is a figure which shows temperature distribution.
If the upper and lower gaps are different, regardless of whether the upper and lower coils 2b and 3b are connected in series or in parallel, the temperature of the plate surface on the side with the smaller gap tends to increase.
FIG. 11 is a diagram showing a ratio of (plate upper surface heat generation density) / (plate lower surface heat generation density) with respect to a ratio of (upper gap) / (lower gap) in the transverse induction heating apparatus in the fourth embodiment. is there.
In FIG. 11, when the upper and lower gaps are different, the temperature rise on the plate surface on the smaller gap side is increased.

As described above, when the upper and lower gaps are different, the temperature rise differs in the thickness direction of the material 1 to be rolled. Therefore, the lifting means 13 so that the vertical gap is the same according to the plate thickness of the material 1 to be rolled. , 14 can adjust the positions of the inductors 2 and 3 so that the temperature rise can be adjusted on the upper and lower surfaces of the plate.
The temperature distribution in the thickness direction of the material to be rolled 1 before passing through the inductors 2 and 3 is the degree of baking by gas heating in the heating furnace and the heat removal to the skid rail (not shown) that supports the material to be rolled 1. Alternatively, the temperature on the lower surface side of the material 1 to be rolled tends to be lower than that on the upper surface side due to heat removal to a conveyance roll (not shown) during the conveyance after extraction from the heating furnace.

Such a temperature difference between the upper and lower surfaces of the material to be rolled 1 may affect variations in plate quality and machinability.
However, according to the above configuration, the upper and lower inductors 2 and 3 are moved up and down by the elevating means 12 and 13 to adjust the gap between the inductors 2 and 3 and the material 1 to be rolled, and the lower gap is changed to the upper gap. By making it smaller, the lower surface of the plate can be heated higher than the upper surface of the plate, so that the upper and lower surfaces of the plate can be made uniform.

Embodiment 5 FIG.
FIG. 12 is a diagram for explaining the configuration and operation of a transverse induction heating system according to Embodiment 5 of the present invention.
The transverse induction heating system according to the present embodiment is characterized in that a plurality of transverse induction heating apparatuses having the configuration according to the first embodiment are arranged from the upstream side to the downstream side of the steel rolling line. To do.
In addition, FIG. 12 has shown the case where the 1st induction heating apparatus 19 is arrange | positioned in the upstream of a steel rolling line, and the 2nd induction heating apparatus 20 is arrange | positioned in the downstream.
12A shows a state in which the tip of the material 17 to be rolled (plate tip) starts to pass between the inductors 19a of the first induction heating device 19, and FIG. The time when the tail end (the plate tail end) starts to pass between the inductors 19a of the first induction heating device 19 is shown.

In FIG. 12, the material to be rolled 17 is conveyed from the left in the figure to the right in the figure by the conveyance rolls 18a to 18c.
A first induction heating device 19 and a second induction heating device 20 are arranged from the upstream of the line in the traveling direction of the material to be rolled 17.
The induction heating devices 19 and 20 each have an individual AC power source (not shown). The frequency of the AC power source (not shown) connected to the induction heating device 19 on the upstream side of the line is F1, and the frequency of the AC power source (not shown) connected to the induction heating device 20 on the downstream side of the line is F2. .

Further, when the frequency of the nth AC power source (not shown) from the upstream side is Fn and K = 1.05 to 1.20, the upstream AC power source (not shown) and the downstream AC power source ( The frequency of (not shown) is set so as to satisfy the following formula (4).
F1> F2 × K>...> Fn × K ^n-1 (4)
The transverse induction heating apparatus has a large impedance in a no-load state where the material to be rolled 17 does not exist between the upper and lower inductors 19a and 20a.
Therefore, when an inverter that operates following the resonance frequency of the load is used as an AC power supply, the frequency is lower than that at the time of loading as shown in FIG.
When the heating frequency of the induction heating device 19 on the upstream side is set lower than the heating frequency of the induction heating device 20 on the downstream side when the tip portion where the material to be rolled 17 has been conveyed from the upstream passes through the inductors 19a and 20a, The heating frequencies of the induction heating device 19 after passing through the tip and the downstream induction heating device 20 passing through the tip of the plate coincide with each other even though they are instantaneous.

For this reason, magnetic interference may occur between the adjacent induction heating devices 19 and 20, and the heating temperature may be unstable, or the power supply may trip.
However, by setting the frequency of the AC power source (not shown) on the upstream side of the line to be higher than the frequency of the AC power source (not shown) on the downstream side, the upstream end of the plate 17 of the material to be rolled 17 is connected to the induction heating device 19. It is possible to prevent the power supply from tripping after passing.

As described above, the transverse induction heating system according to the present embodiment is a transverse type in which a plurality of transverse induction heating apparatuses described in the first embodiment are installed from the upstream side to the downstream side of the steel hot rolling line. In the induction heating system, AC power sources are individually connected to the inductors of a plurality of transverse induction heating devices, and the heating frequency of the individual AC power sources is set to F1, F2,. .. When Fn and K = 1.5-1.20, the relational expression that the heating frequency of each AC power source is “F1> F2 × K>...> Fn × K ^n-1 ” Since it is set so as to satisfy, the frequency of the AC power source on the upstream side of the steel hot rolling line can be made higher than the frequency of the AC power source on the downstream side. Through The power supply it is possible to prevent the trip at a later time.

  This invention realizes a transverse induction heating apparatus or a transverse induction heating system that can heat the plate surface / thickness center in the central part of the plate width of the rolled material substantially uniformly and eliminates excessive heating of the plate surface. Useful.

It is a figure which shows the structure of the transverse type | formula induction heating apparatus in Embodiment 1, and the relationship between the plate width direction distance and average temperature rising value of the to-be-rolled material induction-heated by this apparatus. The ratio (tw / δ) of the plate thickness (tw) to the penetration depth (δ) and the ratio of the heat generation density of the plate surface to the heat generation density at the center of the plate thickness (plate surface / It is a figure which shows the relationship with a board center heat generation density. It is the figure which expanded the principal part of FIG. It is a figure for demonstrating the heat generation density distribution with respect to the plate | board thickness direction of a transverse type and a solenoid type induction heating apparatus. FIG. 6 is a diagram for explaining the configuration and operation of a transverse induction heating apparatus in a second embodiment. It is a figure which shows the plate temperature log | history before and behind the heating by the transverse type induction heating apparatus and solenoid type induction heating apparatus in Embodiment 2. FIG. FIG. 10 is a diagram showing coil connection of a transverse induction heating device in a third embodiment. In the transverse induction heating apparatus in Embodiment 3, it is a figure which shows the electrical loss with respect to the gap of a to-be-rolled material, the iron core of an upper inductor, and the iron core of a lower inductor. FIG. 10 is a diagram showing a configuration of a transverse induction heating device in a fourth embodiment. In the transverse induction heating apparatus in Embodiment 4, it is the figure which showed the temperature increase distribution of the plate | board thickness direction at the time of changing the gap of a to-be-rolled material and the iron core of an inductor. In the transverse induction heating apparatus in Embodiment 4, it is a figure which shows the ratio of (plate upper surface heat generation density) / (plate lower surface heat generation density) with respect to the ratio of (upper gap) / (lower gap). FIG. 10 is a diagram for explaining the configuration and operation of a transverse induction heating system in a fifth embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, Rolled material 2, 3 Inductors 2a, 3a, 9a, 10a Iron core 2b, 3b, 9b, 9c, 10b, 10c Coil 7a, 7b Conveying coil 8 Rolled material 17 Rolled material 18a, 18b, 18c Conveying roll 19 First induction heating device 20 Second induction heating device 19a, 20a Inductor

Claims (9)

An inductor consisting of an iron core and a coil wound around the iron core is arranged so as to face the material to be rolled between the rough rolling mill and finish rolling mill of the steel hot rolling line, and conveyed by a conveying roll. In the transverse induction heating apparatus that heats the material to be rolled by the inductor supplied with electric power from an AC power source,
The core width of the inductor in the plate width direction of the rolled material of the inductor is made smaller than the plate width of the rolled material and is arranged on the plate width center line of the rolled material, and the current penetration depth is δ (m), The specific resistance of the material to be rolled is ρ (Ω-m), the magnetic permeability of the material to be rolled is μ (H / m), the heating frequency of the AC power source is f (Hz), the circumferential ratio is π, and the material to be rolled When the thickness of the material is tw (m),
The heating frequency of the AC power supply is set so that the current penetration depth δ of the following formula (1) satisfies the following formula (2), and the plate surface and the plate thickness center of the plate width central portion of the material to be rolled are A transverse induction heating apparatus characterized by being heated substantially uniformly.
δ = {ρ / (μ · f · π)} ^1/2 (1)
1.0 <{cosh (tw / δ) + cos (tw / δ)} / 2 <1.03 (2)   The transverse induction heating apparatus according to claim 1, wherein the inductor has a plurality of magnetic poles.   The transverse induction heating apparatus according to claim 1 or 2, wherein the coils are connected in series.   4. The transverse induction heating apparatus according to claim 1, wherein each of the inductors is configured to be movable in a direction of a plate thickness of the material to be rolled by an elevating unit. 5. .   The transverse type according to any one of claims 1 to 4, wherein at least two sets of the inductors are arranged in a traveling direction of the material to be rolled, and the conveying rolls are arranged between the inductors. Induction heating device.   6. The transverse induction heating apparatus according to claim 5, wherein the iron core of each inductor is disposed on a plate width center line of the material to be rolled.   The transverse induction heating apparatus according to any one of claims 1 to 6, wherein the transport roll has a surface coated with an electrical insulating member.   The width of the core of each of the inductors is set to be equal to or less than the value obtained by subtracting 300 mm from the plate width of the material to be rolled, and in the direction parallel to the plate surface of the material to be rolled, The transverse induction heating apparatus according to claim 6, wherein a distance between the outer peripheral surfaces of each of the plurality of outer circumferential surfaces is 150 mm or more. A transverse induction heating system in which a plurality of transverse induction heating devices according to claim 1 are installed from upstream to downstream of the steel hot rolling line,
An AC power source is individually connected to each of the inductors of the plurality of transverse induction heating devices, and the heating frequency of the individual AC power source is set to F1, F2,... Fn from the upstream side of the steel hot rolling line, and , When K = 1.5-1.20, the heating frequency of each AC power source is
F1> F2 × K>...> Fn × K ⁿ⁻¹
A transverse type induction heating system characterized by being set to satisfy the relational expression of

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